Electronic user interface and method for controlling precision guided firing of a rifle

ABSTRACT

A rifle scope includes an image sensor configured to capture visual data corresponding to a view area, a display, and a controller coupled to the display and the image sensor. The controller is configured to apply a first stabilization parameter to at least a portion of the visual data to produce a stabilized view, to provide the stabilized view and a reticle to the display, and to apply a second stabilization parameter to stabilize the reticle relative to the stabilized view in response to motion.

FIELD

The present disclosure is generally related to precision guided firearmsand more particularly to methods for precision firing of a gun.

BACKGROUND

A precision guided firearm includes a rifle or other firearm and anintelligent digital optical scope that integrates with, and controls thefiring of, the precision guided firearm. The precision guided firearmallows a user to designate or tag a target prior to actually firing onthe target, calculates range to the target, and calculates the properballistic solution for accurately impacting the target. Once a target istagged, the intelligent digital optical scope portion of the precisionguided firearm tracks the target location relative to the barrelposition and delays firing until the firearm's barrel is in the properposition to ensure the firearm fires on target based on the calculatedballistic solution.

Designating or tagging a target with a precision guided firearm in thepresence of human jitter can be difficult. In particular, telescopicdevices magnify the jitter, making it difficult to accurately designatethe target.

SUMMARY

In an embodiment, a rifle scope includes an image sensor configured tocapture visual data corresponding to a view area, a display, and acontroller coupled to the display and the image sensor. The controlleris configured to apply a first stabilization parameter to at least aportion of the visual data to produce a stabilized view, to provide thestabilized view and a reticle to the display, and to apply a secondstabilization parameter to stabilize the reticle relative to thestabilized view in response to motion.

In another embodiment, a method includes applying a first stabilizationparameter to visual data corresponding to a view area of a rifle scopeto produce a stabilized portion of the view area. The method furtherincludes applying a second stabilization parameter to independentlystabilize movement of a reticle provided to the display and providingthe stabilized portion and the reticle to a display of the rifle scope.Additionally, the method includes determining a location associated witha target within the stabilized portion corresponding to an aimpoint ofthe reticle relative to the stabilized portion.

In still another embodiment, a viewing device includes one or more imagesensors to capture visual data of a view area, a display, and acontroller coupled to the display and to the one or more image sensors.The controller is configured to provide a visual representation of aportion of a view area and a reticle to the display, to stabilize thevisual representation according to a first stabilization parameter, andto stabilize the reticle according to a second stabilization parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a viewing deviceincluding circuitry configured to range and tag a target.

FIG. 2 is a front-view of the viewing device of FIG. 1.

FIG. 3 is a side-view of an embodiment of a firearm system including theviewing device of FIG. 1 implemented as a rifle scope.

FIG. 4 is a block diagram of an embodiment of a firearm system, such asthe firearm system of FIG. 3.

FIG. 5 is a block diagram of an embodiment of a circuit configured torange and tag a target.

FIG. 6 is a flow diagram of an embodiment of a method of tagging atarget using the telescopic device of FIGS. 1-4 and/or the circuit ofFIG. 5.

In the following discussion, the same reference numbers are used in thevarious embodiments to indicate the same or similar elements.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of a viewing device, such as a rifle scope, are describedbelow that assist the user in selecting a target within a view area,even in the presence of jitter. The viewing device includes a display, acontroller, and one or more image sensors to capture visual dataassociated with a view area that is larger than that presented to thedisplay. The controller is configured to apply a first stabilizationparameter to at least a portion of the visual data to produce astabilized portion and to provide the stabilized portion to the display.The controller is further configured to generate a reticle, to apply asecond stabilization parameter to the reticle, and to provide thestabilized reticle to the display. The first and second stabilizationparameters dampen the effect of the user's movements with respect to therelative movement of the reticle and the portion of the view area,reducing the effect of jitter to assist the user in aiming at andselecting a target. The controller may then apply a visual marker or tagto the selected target in response to explicit user input (such as abutton press), implicit user input (such as detection of directed aimingby a user where the user aims the viewing device at a target for aperiod of time), or automatic target selection.

In one possible example, the viewing device includes a button accessibleby a user to initiate a target selection operation. In response to theuser pressing the button, the controller applies the first stabilizationparameter to a portion of the visual data and applies a secondstabilization parameter to the reticle. Viewing device may include oneor more motion sensors configured to detect changes in the orientationof the viewing device and to alter at least one of the portion of thevisual data provided to the display according to the first stabilizationparameter and the relative position of the reticle according to thesecond stabilization parameter in response to detecting the changes. Thecontroller may then apply the visual marker or tag in response to theuser releasing the button, or in response to detection of a directedaiming event relative to the target within the portion of the viewingarea. Alternatively, image sensors may be used to detect the changes inorientation.

In another example, the controller detects directed aiming by the userwhere the user directs the viewing device toward a particular target fora period of time. In the presence of jitter, the aimpoint of thedirected aiming may be at a center of a plurality of aimpoint data. Inresponse to detecting the directed aiming by the user, the controllermay select a target and apply a visual marker or tag within the displayat a position corresponding to the selected target. In an alternativeexample, the controller may automatically select a target. In oneinstance, the controller may use image processing to detect a targetwithin the view area and apply a visual marker or tag to the selectedtarget. One possible embodiment of a viewing device that includescircuitry configured to stabilize a portion of the view area and areticle using first and second stabilization parameters is describedbelow with respect to FIG. 1.

FIG. 1 is a perspective view of an embodiment of a viewing device 100including circuitry configured to range and tag a target. Viewing device100 may be implemented as a spotting scope, a rifle scope, or anotherviewing device capable of providing a telescopic view of a view area. Asused herein, the term “tag” refers to a visual marker or tag that can beapplied to a selected target within a portion of the view area shown ona display, and not actually applied to the physical target. Further, asused herein, the term “tagging” refers to the application of the tag orvisual marker to the target within the portion of a view area shown on adisplay.

Viewing device 100 includes an eyepiece 102 through which a user maylook to see a portion of a view area on the display. Viewing device 100includes at least one image sensor configured to capture visual datacorresponding to a view area. Viewing device 100 further includes ahousing 104 that defines an enclosure sized to secure the circuitry(including a display), environmental parameter sensors, the imagesensor(s), and laser range finder circuitry, including a transmitterportion (generally indicated at 112) and a receiver portion 114. Viewingdevice 100 further includes a lens portion 110 including an objectivelens 108 for focusing light toward the image sensors.

Viewing device 100 is configured to stabilize the portion of the viewarea according to a first stabilization parameter and to stabilize areticle according to a second stabilization parameter, for example,during a target selection operation. By stabilizing the view area andthe reticle, viewing device 100 makes it easier for a user to direct theaimpoint at a target and to select the target. The portion of the viewarea and the reticle are stabilized independent of one another. In someinstances, the first and second stabilization parameters may besubstantially equal. The viewing device 100 includes one or more buttonsand/or motion sensors configured to receive explicit or implicit userinput for selecting a target within the portion of the view areaprovided to the display. One possible example of an embodiment of theviewing device including one or more buttons and other indicators isdepicted in FIG. 2.

FIG. 2 is a front-view 200 of an embodiment of the viewing device 100 ofFIG. 1. In addition to eyepiece 102, viewing device 100 includes aplurality of indicators, generally indicated at 202, which can, forexample, depict a current battery charge, a status of a connection toassociated circuitry (such as circuitry within a trigger assembly),environmental conditions, and so on. Such indicators may also includeuser-selectable buttons. Additionally, front-view 200 includes a powerbutton 204 that can be accessed by the user to turn viewing device 100on or off. Other buttons or indicators may also be included, such as atarget tag/range finder button, various mode buttons, or otherselectable elements. Further, within the front-view 200, mounting rails,such as rail 206, are visible. Mounting rails 206 are configurable toreleasably attach to a structure, such as a corresponding mountingstructure of a firearm.

In a particular embodiment, viewing device 100 may be attached to afirearm and configured to operate as a rifle scope. An example of theviewing device 100 configured to operate as a rifle scope to provide acomponent of a precision guided firearm is described below with respectto FIG. 3.

FIG. 3 is a side-view of an embodiment of a firearm 300 includingviewing device 100 configured to house circuitry 302. Circuitry 302 isconfigured to stabilize a portion of a view area within a display, tostabilize a reticle, to tag a target within the stabilized portion, andto range the selected target. Viewing device 100 may include one or morebuttons with which a user may interact to initiate target selectionand/or to select a target. Alternatively, viewing device 100 may receivesignals from other sources, such as a button 308 on a grip 306 of arifle 304 or from a portable computing device, such as a tablet computeror smart phone. Circuitry 302 may be coupled to a trigger assembly 310to provide a precision-guided firearm.

Circuitry 302 is configured to capture optical data associated with aview area and to provide a visual representation of a portion of theview area and a reticle to the display. In general, circuitry 302captures optical data corresponding to an area that is larger than theportion provided to the display. Circuitry 302 stabilizes the portion ofthe view area using a first stabilization parameter, stabilizes areticle using a second stabilization parameter, and provides thestabilized portion and the reticle to a display. In response to a targetselection signal, circuitry 302 may apply a visual marker to a selectedtarget within the view area. The target may be selected by a user bypressing button 308 or some other button on viewing device 100.Alternatively, the target may be selected automatically and/or inresponse to directed aiming by the user.

In general, the above-described functionality can be implemented by avariety of circuits. One possible example of an embodiment of circuitry302 is described below with respect to FIG. 4.

FIG. 4 is a block diagram of an embodiment of a firearm system 400, suchas the firearm system 300 of FIG. 3, including a controller 402, adisplay 404, motion sensors 406, and image sensors 410. Controller 402may be implemented as a circuit. Alternatively, controller 402 may beimplemented as a processor configured to execute instructions stored ina data storage medium.

Image sensors 410 capture optical data associated with a view area 412and provide the optical data to controller 402. Controller 402 iscoupled to display 404 to provide a visual representation of a portionof a view area (corresponding to a subset of the optical data) and toprovide a reticle, which can be presented in front of the portion of theview area. Firearm system 400 includes one or more motion sensors 406(such as gyroscopes, inclinometers, accelerometers, and the like)coupled to controller 402 to provide orientation and motion data thatcan be used by controller 402 to determine an aimpoint of the firearmsystem 400.

Firearm system 400 further includes one or more user-selectable inputelements 408, such as input/output ports or input terminals configuredto receive signals from one or more buttons or switches for receivinguser selections and/or user inputs (i.e., signals). In some instances,user-selectable input elements 408 can include a transceiver for sendingand receiving data, including user inputs, such as through a wired orwireless communication link. In an example, the transceiver can be usedto receive a target-selection input from a portable computing device,such as a laptop, tablet, smart phone, or other portable computingsystem.

Firearm system 400 includes controller 402 configured to apply a firststabilization parameter to a portion of the optical data correspondingto a field of view of viewing device 100 and a second stabilizationparameter to a reticle. Application of the first and secondstabilization parameters dampens the relative movement of the reticleand the portion of the optical data of the view area to assist the userin directing the aimpoint toward the target and in selecting the target.

Controller 402 may be implemented as circuitry including a fieldprogrammable gate array, as a processor with a memory storing executableinstructions, or any combination thereof. One possible example ofcontroller 402 implemented as a processor and a memory is describedbelow with respect to FIG. 5.

FIG. 5 is a block diagram of an embodiment of circuitry 302 of FIG. 3(or controller 402 of FIG. 4). Circuitry 302 includes a processor 501coupled to a memory and logic circuit 502. Memory and logic circuit 502stores instructions that, when executed by processor 501, causeprocessor to function as controller 402 in FIG. 4. Circuitry 302 furtherincludes display 404 and motion sensors 406 coupled to processor 501. Insome instances, motion sensors 406 may include an analog-to-digitalconverter (ADC) to convert analog sensor signals into digital signalsfor processor 501. In other instances, circuitry 302 may include an ADCbetween motion sensors 406 and processor 501.

Circuitry 302 is coupled to trigger assembly 310 and to one or moreuser-selectable input elements 408. Circuitry 302 includes a triggerassembly interface 504 coupled to trigger assembly 310 to receive and/ordetect a trigger pull signal. Circuitry 302 further includes a targetselection input interface 508 coupled to user-selectable input elements408 and configured to receive signals corresponding to user-selectionsof one or more of the user-selectable input elements 408 (such asbuttons or switches) for manual target acquisition and range findingselection. Circuitry 302 further includes image sensors 410 configuredto capture optical data associated with a view area 412. Triggerassembly interface 504, target selection input interface 508, and imagesensors 410 are coupled to processor 501. Circuitry 302 further includeslaser range finder circuitry 510 coupled to processor 501 and to laserinterface 512 and laser range finder (LRF) optical sensor(s) 514.

Motion sensors 406 include one or more inclinometers 516 to detect anincline or orientation of the viewing device 100. Motion sensors 406further include one or more gyroscopes 518 to determine orientation ofthe viewing device 100 based on principles of angular momentum. Further,motion sensors 406 include one or more accelerometers 520 configured tomeasure movement of viewing device 100. Motion sensors 406 may alsoinclude other motion sensor circuitry 522 that can be used to measuremovement and/or to determine the orientation of viewing device 100.Motion sensors 406 provide such movement and/or orientation data toprocessor 501.

Memory and logic circuit 502 is a processor-readable data storage mediumthat stores instructions executable by processor 501 to stabilize aportion of the optical data corresponding to view area 412 that iscaptured by image sensors 410, to stabilize a reticle that is providedto display 404 with the stabilized portion of the optical data, toreceive a target selection signal, and to apply a visual marker to aselected target in response to the target selection signal, which may beprovided automatically, determined from implicit user feedback, orprovided by an explicit user input.

Memory and logic circuit 502 includes button detection logic 530, thatwhen executed, causes processor 501 to detect a button press and/or abutton release. In an example, the button press corresponds to pressingof a target selection button 308 on the grip 306 of the rifle 304. Inanother example, the button press corresponds to pressing of a targetselection button on viewing device 100, such as one of the buttons orindicators 202. Additionally, memory and logic circuit 502 includesimplicit user-input detection logic 540 that, when executed, causesprocessor 501 to detect implicit user input (such as directed aiming)and to select a target in response to the implicit user input.

Memory and logic circuit 502 further includes laser range finder (LRF)control instructions 532 that are executable by processor 501 to controllaser range finding circuitry 510 to fire a laser beam toward a target(using laser interface 512) and to receive a reflected version of thelaser beam from the target (via LRF optical sensors 514) to determine arange to the target. Processor 501 may execute LRF control instructions532 in response to a button push and/or in response to automatic oruser-selection of a target. Memory and logic circuit 502 also includesstabilizer 534 that, when executed, causes processor 501 to stabilize aportion of the optical data of view area 412 received from image sensors410. Memory and logic circuit 502 further includes reticle generatorinstructions 538 that, when executed, cause processor 501 to generate areticle, which is provided to display 404 together with the stabilizedportion of the view area. Stabilizer 534 may be used to stabilize thereticle using the same or a different stabilization parameter ascompared to that used to stabilize the portion of view area 412.

Memory and logic circuit 502 further includes image processing logic 536that, when executed, causes processor 501 to automatically processimages (optical data) from the image sensors 410 to detect boundaries,to identify targets, etc. In one instance, processor 501 executes imageprocessing logic 536 to automatically identify a target within a portionof the view area, such as by detecting localized motion and identifyingboundaries of the target automatically. In some instances, processor 501may execute image processing logic 536 to detect a change in theorientation of viewing device 100 relative to the view area based onchanges in the optical data from image sensors 410 over time.

Memory and logic circuit 502 further includes a target tagger 542 that,when executed, causes processor 501 to apply a visual tag to a target atthe center of the reticle, in response to a button press, a buttonrelease, implicit user feedback, or some combination thereof. In someimplementations, target tagger 542 may automatically select a targetusing image processing logic 536 to detect the target and mayautomatically apply a visual tag to the selected target. Memory andlogic circuit 502 also stores one or more view area stabilizationparameters 544 and one or more reticle stabilization parameters 546,which can be applied by stabilizer 534 to stabilize the portion of theview area and the reticle, respectively. In some instances, stabilizer534 may select a suitable stabilization parameter, for example, based onthe zoom. In this example, zoom refers to the electronic emulation ofadjustable focal length. At greater levels of zoom, it may be desirableto dampen the effect of the user's movements by a greater amount,increasing the stabilization to reduce the effect of jitter for both theportion of the view area and the reticle, independently.

In an example that could involve either explicit user input, implicituser input, or automatic target selection and ranging, circuitry 302receives a signal at target selection input interface 314 thatcorresponds to receiving a target selection signal. The target selectionsignal may be received from an input interface or may be provided byprocessor 501 (either based on detection of “directed aiming” by theuser or based on automatic target selection). In response to receivingthe signal, circuitry 302 may automatically range the target or the viewarea 412 using LRF control instructions 532. Alternatively or inaddition to ranging the target, in response to receiving the signal,circuitry 302 stabilizes a portion of the view area and a reticleprovided to display 404. Circuitry 302 then either uses motion data frommotion sensors 406 or processes images from the view area to determinean orientation of viewing device 100 relative to the view area todetermine an aimpoint relative to the stabilized portion. The stabilizer534 dampens the effect of the user's movement, steadying the view areaand the reticle in the presence of jitter to assist the user to positionthe reticle on a target within the stabilized portion of view area 412.In response to a second signal, circuitry 302 attaches a visual markeror tag to the selected target within the stabilized portion.

In one embodiment, circuitry 302 detects a first signal when the buttonis pressed and uses stabilizer 534 to stabilize the portion of the viewarea 412 and the reticle in response to the first signal. Circuitry 302detects a second signal when the button is released and applies thevisual marker to the target in response to the second signal. In someexamples, the first and second signals may be of the same type and/ormagnitude or may be of opposite polarity. In another embodiment, laserrange finding and target selection may be initiated through interactionwith a touch-sensitive interface provided either on a surface of riflescope 302, on the grip of the rifle 304, or on a portable computingdevice, such as a smart phone or tablet computer configured tocommunicate with viewing device 100. One possible example of a method ofoperating the viewing device 100 to visually tag (apply a visual markerto) a selected target is described below with respect to FIG. 6.

FIG. 6 is a flow diagram of an embodiment of a method 600 of tagging atarget using the telescopic device of FIGS. 1-4 and/or the circuit ofFIG. 5. At 602, a visual representation of a portion of a view area of atelescopic device is provided to a display, where the visualrepresentation includes a reticle. Advancing to 604, a target taggingoperation is initiated in response to receiving a signal. The signal maycorrespond to explicit user input (such as a button press), implicituser input (such as detection of directed aiming by the user), orautomatic target selection. Continuing to 606, controller 402 stabilizesa portion of the view area using a first stabilization parameter andstabilizes a reticle using a second stabilization parameter. The firstand second stabilization parameters may be the same. In some instances,controller 402 may select a first suitable stabilization parameter forthe view area 412 based and may select a second suitable stabilizationparameter for the reticle.

Moving to 608, controller 402 determines movement of viewing device 100relative to view area 412. In an example, controller 402 uses motiondata from motion sensors 406 to determine movement of viewing device 100in order to determine the aimpoint. In another example, controller 402uses image processing logic 536 to determine movement of viewing device100 relative to view area 412 to determine the aimpoint.

Proceeding to 610, controller 412 adjusts at least one of the stabilizedportion of the view area behind the reticle and the position of thereticle relative to the stabilized portion of the view area in responseto determining the movement. In an example, the user's movements may bedampened or filtered (digitally) to reduce jitter and to assist the userto align the center of the reticle to the desired target.

Continuing to 612, controller 402 applies a visual marker or tag to theselected target. In one instance, controller 402 receives a buttonrelease signal and applies the visual marker to the selected target inresponse to the button release signal. In another instance, controller402 detects directed aiming by the user and applies the visual marker inresponse to detecting the directed aiming. In another instance,controller 402 receives an automatic target selection signal and appliesthe visual marker in response thereto.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the scopeof the invention.

What is claimed is:
 1. A rifle scope comprising: an image sensorconfigured to capture visual data corresponding to a view area; adisplay; and a controller coupled to the display and the image sensor,the controller, in a target selection mode, configured to apply a firststabilization parameter to at least a portion of the visual data toproduce a stabilized view, to provide the stabilized view and a reticleto the display, and to apply a second stabilization parameter tostabilize the reticle to dampen movement of an aimpoint corresponding tothe reticle relative to the stabilized view in response to motion. 2.The rifle scope of claim 1, further comprising: an input interfaceconfigured to receive a signal corresponding to a user interaction witha button; and wherein the controller is configured to determine alocation of a target within the stabilized view in response to receivingthe signal.
 3. The rifle scope of claim 2, wherein the controller isconfigured to apply a visual marker to the target within the stabilizedview.
 4. The rifle scope of claim 1, wherein the controller isconfigured to determine motion data, to detect a directed aiming eventbased on the motion data, and to automatically select a target inresponse to detecting the directed aiming event.
 5. The rifle scope ofclaim 4, wherein the controller automatically applies a visual marker tothe target.
 6. The rifle scope of claim 1, further comprising: at leastone motion sensor coupled to the controller and configured to detectchanges in an orientation of the image sensor; and wherein thecontroller is configured to stabilize movement of the reticle relativeto the stabilized view in response to detecting the changes.
 7. Therifle scope of claim 1, wherein: the controller is configured to detectchanges in an orientation of the image sensor by processing the visualdata of the view area to determine an orientation of the image sensor;and the controller is configured to stabilize movement of the reticlerelative to the stabilized view in response to detecting the changes. 8.The rifle scope of claim 1, wherein the first stabilization parameterand the second stabilization parameter are substantially equal.
 9. Amethod comprising: applying, in a target selection mode, a firststabilization parameter to visual data corresponding to a view area of arifle scope to produce a stabilized portion of the view area; applying,in the target selection mode, a second stabilization parameter toindependently stabilize movement of a reticle to dampen movement of anaimpoint corresponding to the reticle relative to the stabilizedportion; providing the stabilized portion and the reticle to a displayof the rifle scope; and determining a location associated with a targetwithin the stabilized portion corresponding to the aimpoint of thereticle relative to the stabilized portion.
 10. The method of claim 9,wherein determining the location associated with the target comprises:detecting a directed aiming event based on motion data from one or moremotion sensors; and automatically selecting a target in response todetecting the directed aiming event.
 11. The method of claim 9, whereindetermining the location associated with the target comprises: detectinga directed aiming event based on image processing; and automaticallyselecting a target in response to detecting the directed aiming event.12. The method of claim 9, further comprising applying a visual markerto the target within the stabilized portion in response to determiningthe location associated with the target.
 13. The method of claim 9,wherein determining the location associated with the target comprises:receiving a target selection signal at an interface; and determining thelocation based on a position of the reticle relative to the stabilizedportion when the target selection signal is received.
 14. The method ofclaim 13, wherein the target selection signal comprises at least one ofa button press and a button release.
 15. The method of claim 13, whereindetermining the location comprises image processing the stabilizedportion to automatically identify the location of the target.
 16. Themethod of claim 9, wherein the first stabilization parameter and thesecond stabilization parameter are substantially equal.
 17. A viewingdevice comprising: one or more image sensors to capture visual data of aview area; a display; and a controller coupled to the display and to theone or more image sensors, the controller configured to provide a visualrepresentation of a portion of the visual data and a reticle to thedisplay, the controller configured to stabilize the visualrepresentation according to a first stabilization parameter and tostabilize the reticle according to a second stabilization parameter todampen movement of an aimpoint corresponding to the reticle relative tothe stabilized visual representation.
 18. The viewing device of claim17, further comprising: one or more motion sensors configured to detectmotion data of the viewing device; and wherein the controller isconfigured to adjust at least one of the portion provided to the displayand a position of the reticle relative to the portion according to thesecond stabilization parameter in response to detecting the motion data.19. The viewing device of claim 18, wherein the controller is configuredto detect a directed aiming event based on the motion data, toautomatically select a target in response to detecting the directedaiming event, and to automatically apply a visual marker to the target.20. The viewing device of claim 17, wherein the controller is configuredto: process the visual data to determine an orientation of the viewingdevice relative to the visual representation; and adjust at least one ofthe portion provided to the display and a position of the reticlerelative to the portion according to the second stabilization parameterin response to determining the orientation.
 21. The viewing device ofclaim 17, wherein the controller receives a signal corresponding toselection of a target location within the portion of the view area andapplies a visual marker to a target at the target location in responseto receiving the signal.
 22. The viewing device of claim 21, furthercomprising: an interface configured to receive the signal; and whereinthe signal corresponds to at least one of a button press and a buttonrelease.
 23. The viewing device of claim 17, wherein the firststabilization parameter and the second stabilization parameter aresubstantially equal.